KT advertised 5G at 20Gbps — real speeds were 3% of that, and the fine stands

From August 2018 to April 2022, KT — one of South Korea's three big mobile carriers — advertised 5G speeds of '20Gbps' and '20x faster than LTE' on its homepage, YouTube and posters. Comparison posters went further: definitive claims of leading nationwide, with specific speed figures for eleven regions and no objective basis behind them.

The KFTC found actual speeds were about 3% of the advertised 20Gbps — nowhere near 20x LTE — and in 2023 fined KT ₩13.93 billion for false, exaggerated and deceptive advertising. KT sued, arguing the ads described technical characteristics rather than guaranteed speeds, and that consumers of ordinary attention would grasp the limits. On 16 July 2026 the Seoul High Court rejected that: 20Gbps cannot be realised in actual usage environments, and consumers — unable to verify speeds without specialist equipment — read the numbers as the service they would actually get.

The comparison posters were separately misleading, the court held: definitive wording and hard figures made unproven claims look like established fact, and the surcharge calculation was lawful. KT filed a Supreme Court appeal on 23 July 2026. In the parallel cases, LG U+ also lost over its ₩2.85 billion fine, while SK Telecom won a partial reduction of its ₩16.83 billion penalty.